CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Alliance revenue	$ 164	$ 323	$ 729	$ 918
Operating expenses:
Research and development	10,912	9,393	40,288	28,817
General and administrative	3,919	3,907	11,888	11,601
Total operating expenses	14,831	13,300	52,176	40,418
Loss from operations	(14,667)	(12,977)	(51,447)	(39,500)
Other income (expense):
Interest income	159	90	456	320
Interest expense	(11)	(19)	(40)	(63)
Foreign currency exchange (loss) gain	(11)	3	(27)	32
Net loss	$ (14,530)	$ (12,903)	$ (51,058)	$ (39,211)
Basic and diluted net loss per common share (Note 14)	$ (0.10)	$ (0.10)	$ (0.34)	$ (0.32)
Shares used in computing basic and diluted net loss per common share	149,638	121,389	149,385	121,332
Net loss	$ (14,530)	$ (12,903)	$ (51,058)	$ (39,211)
Other comprehensive gain (loss):
Unrealized (loss) gain on available-for-sale securities	(1)	13	17	133
Comprehensive loss	$ (14,531)	$ (12,890)	$ (51,041)	$ (39,078)